On 24 Aug 2013, at 22:13, Norbert Lindenberg <[email protected]> wrote:
> On Aug 24, 2013, at 2:02 , Mathias Bynens <[email protected]> wrote: > >> On 27 Feb 2012, at 22:58, Allen Wirfs-Brock <[email protected]> wrote: > >>> var \ud87e\udc00 would probably still be illegal because each \uXXXX define >>> a separate character but: var \u{2f800} =42; schould be find as should the >>> direct none escaped occurrence of that characters. >> >> Wouldn’t this be confusing, though? >> >> global['\u{2F800}'] = 42; // would work (compatible with ES5 behavior) >> global['\uD87E\uDC00'] = 42; // would work, too, since `'\uD87E\uDC00' == >> '\u{2F800}'` (compatible with ES5 behavior) >> var \uD87E\uDC00 = 42; // would fail (compatible with ES5 behavior) >> var \u{2F800} = 42; // would work (as per your comment; incompatible with >> ES5 behavior) >> var 丽 = 42; // would work (as per your comment; incompatible with ES5 >> behavior) > > I do think it's confusing that \uD87E\uDC00 is not allowed in the current ES6 > spec, and have reported this as part 4 of > https://bugs.ecmascript.org/show_bug.cgi?id=501 Agreed. It would make much more sense to just treat `\u{2F800}` and `\uD87E\uDC00` exactly the same way, even outside of string contexts. > The issue was also discussed, without a conclusion, at the TC 39 meeting in > July 2012 - look for "# Unicode support": > https://mail.mozilla.org/pipermail/es-discuss/2012-July/024207.html > >> Using astral symbols in identifiers would be backwards incompatible, even if >> the raw (unescaped) symbol is used. There’d be no way to use such an >> identifier in an ES5 environment. Is this a problem? > > It's the same problem as when using > let a = 42; > > You should not expect that a program using new ES6 features will run on ES5 > implementations (although it might run on some that have already added the > ES6 features used). I just want to make sure it’s possible to write a polyfill (in ES5) for the `String.isIdentifier{Start,Part}` strawman. As long as `String.isIdentifierStart('\uD87E\uDC00')` and `String.isIdentifierStart('\u{2F800}')` are expected to return different results (as Allen suggests), this is impossible. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
